Information supplied by the internet giant Yahoo! to Chinese intelligence has resulted in the conviction of a journalist for "divulging state secrets abroad", a respected international press organisation said.

Shi Tao, who worked for the daily business publication Dangdai Shang Bao (Contemporary Business News) until he was arrested in November 2004, was sentenced to 10 years in prison last April, in a case underlining the stringent censorship regime which controls the Chinese media.

He was convicted of sending foreign-based websites the text of a "top secret" government message that had been sent to his newspaper. The text warned Chinese journalists of the dangers of social destabilisation and risks resulting from the return of certain dissidents on the 15th anniversary of the Tiananmen Square massacre.

According to Reporters Without Borders (RSF), the text of the verdict on Mr Shi indicated that Yahoo! willingly handed over details which enabled security service investigators to link the journalist's personal e-mail account to to the anonymous message.

The US multinational Yahoo! allows the Chinese version of its search engine to be censored - it bars any mention of the Free Tibet campaign, for example - and critics say it is willing to stifle free speech in order to gain access to the lucrative Chinese market.

In 2003, Yahoo! invested $120m to purchase a Chinese-owned search engine. 3721.com. More recently, it acquired a large stake in the internet giant Alibaba in an operation that reportedly cost nearly a billion dollars.

"Yahoo! obviously complied with requests from the Chinese authorities to furnish information regarding an IP address that linked Shi Tao to materials posted online, and the company will yet again simply state that they just conform to the laws of the countries in which they operate," RSF said.

Mr Shi was sent to a prison in Changsha province, where he remains today, on the grounds that the information he made available was "Jue Mi" - a state secret. Mr Shi admitted he had sent a message from the authorities to foreign-based websites but denied it was compulsory to keep the document secret.

"Information supplied by Yahoo! led to the conviction of a good journalist who has paid dearly for trying to get the news out," RSF said. "It is one thing to turn a blind eye to Chinese government abuses but it is quite another thing to collaborate."

Yahoo! Hong Kong is subject to the domestic legislation of the former British colony, which does not spell out the responsibilities of companies in sensitive situations such as this. But it is reportedly common practice for e-mail and internet service providers to transmit information to the police about their clients when demanded by a court order.

RSF said it had written to Yahoo! to alert it to the "ethical issues raised by its Chinese investments" but there had been no reply.